I found a WaringPro Dehydrator WDHR60SILPC at the thrift store and needed a riser to fit a filament spool inside without cutting it up. 

The tray measurements (outside) are:

• 335 mm long axis (between flats)
• 320 mm narrow axis
• 75 mm flats on the ends

You will need two each of part 1 and part 2, as they are mirror images of each other. I can fit one of each on my printer (Sovol SV06) YMMV.

Print single edge down with "baseplate only" rectangular supports. The supports came off cleanly for me. 

You will want to use a couple of lengths of filament for keying the parts together when you glue it. About 20mm each will be fine. You will need 8 lengths.